Various types of simple usual profiles are already used.
The effort perpendicular to the fin plane which produces the stabilizing effect is characterized by a coefficient of lift usually called Cz.
This effort is expressed by the formula: EQU L=1/2.rho.Cz S V.sup.2
where
.rho.is the density of the ambient medium PA1 S the surface of the fin PA1 V the displacement speed of the profile in the ambient medium (generally the speed of the ship provided with the stabilizers) (see FIG. 1) PA1 the pairs of fixed flaps are placed symmetrically on the lower and upper faces of the main fin to which they are fixedly connected; PA1 the pairs of flaps respectively situated on the lower and upper sides of the main fin are placed near the trailing edge of said main fin so that the tangents to their mean camber at the leading edge, or inclined, are substantially parallel to the mean plane of the main fin; yet dispositions other than tangent at the leading edge parallel to the fin plane can also be envisaged (inclined tangents) as a function of the performances; PA1 the main fin is provided at its ends with plane plates to which are fixed the ends of the pairs of fixed flaps; PA1 the connection of the pairs of flaps with the main fin is obtained by means of plates to which struts can be associated; PA1 the assembly formed by the main fin, the flaps, the plates and the struts constitutes the stabilizing fin as such and this fin is inclined with respect to the water streams by any known means with the assistance of an axis; yet, the fin can be used as a fixed plane and not be orientable, which is the case of passive stabilizing planes or damping devices; PA1 the devices is implemented for known roll stabilizers of the collapsible or non collapsible type. The fin can be used for anti-pitch dispositions, anti-roll devices, steering apparatus, submarine diving bars, and any ship steering or stabilizing device. This type of fin can also Be used on any civil (mono-hull, multi-hull, swath, wave pearcer), pleasure or war ship.
The Cz coefficient varies according to FIG. 2 as a function of the inclination of the fin in the water streams. The Zo portion of the curve corresponds to the stalling zone corresponding to a loss of lift.
So, one sees that for a given effort and a given speed, the surface of the fin will be all the smaller that the Cz will be higher.
Yet, the surfaces of the fins determine their weight and therefore the stabilizers prices. Moreover, when the fins are collapsible, they determine what is called an additional floatability loss, meaning the water volumes of the hull housings in which the fins are stored when the weather is good.
All these technical and cost elements are taken in account in the performances and in the price of the ship which they fit out.
Therefore, the ship builders have done their best to use profiles having Cz's as high as possible. In the ascending order of the Cz's, one finds:
Standard simple profiles having the advantage of a simple structure and a simple fin control mechanism. The resistance to progression in water is small, but the effect of the small Cz is that this fin type is generally only used for fins of small surfaces. An example of a profile of this type is shown in FIGS. 1 and 3.
A "fish" type profile to which can be added a plate at the end of the fin. This profile improves the Cz but has the disadvantage of generating noises and vibrations. In addition, the resistance to progression is increased. One example of a profile of this type is shown in FIG. 4.
A profile with camber flap. In this case, it is a profile including a main fin at the trailing edge of which is articulated a camber flap. The articulation is such that to any angle .alpha. of the main fin corresponds an angle .beta. of the flap.
The articulation of the flap on the main fin is provided by any known mechanisms (pinions, connecting rods, etc.). The Cz is improved but the installation is complex and costly since the articulation is continuously immersed in sea water. In some cases, this articulation can form a limit for the fin surface since the deformations of the fin in operation and due to the deflection can be incompatible with such an articulation. In addition, the resistance to progression is high and can have a brutal stalling characteristic, in the same way as with the "fish" type profile. An example of this type of profile is shown in FIG. 5.
The effect of this invention is to increase the Cz to a value which is substantially higher than that of a profile with a camber flap, while preserving a simple structure and a resistance to progression which is less or at most equal to that of a "fish" type profile or of a camber flap, and this whatever the fin span/mean chord utilization ratio.